Many types of sophisticated electronic equipment utilize modular circuit boards mounted into a housing or mounting frame. The mounting frame provides a secure enclosure which protects the delicate circuit components and organizes the various circuit boards within a compact space.
For example, many of the different devices utilized in audio/video broadcasting are built into circuit boards that are mounted into one or more mounting frames in, for example, a television broadcast studio or post-production facility. Each circuit board is provided with circuitry designed to perform the particular function(s) of the device. In the case of audio/video equipment these might include distribution amplifiers, routing switchers, sync pulse and test signal generators, time code readers, logo generators, analog-to-digital converters etc.
In such applications the circuitry on each circuit board requires both internal connections for interfacing with power supplies and other circuit boards, and external connections for interfacing with external devices. These connections are typically detachable to provide a modular design. Each circuit board is supported in a compartment within the mounting frame. Typically internal connections include communications busses for high speed data communication between circuit boards within the mounting frame, and power conductors for supplying power to the circuit boards, often from multiple power supplies operating at different voltage levels. These busses and conductors can be supported on a board or "back plane" extending across the mounting frame through the circuit board compartments.
External connections typically include standard cable connectors for the detachable connection of cables transmitting signals to, or receiving signals from, external equipment such as cameras, receivers, mixers, computers etc. The rear edge of each circuit board is exposed through an opening in the rear of the mounting frame, and thus the cable connectors for external connections are fastened along the rear edges of the circuit boards so as to be accessible.
In conventional mounting systems rectangular circuit boards for each device are mounted in the mounting frame by sliding circuit boards lengthwise into the front of the mounting frame, into channels or tracks disposed along each compartment. A row of contacts along the rear edge of the circuit board mates with a connector supported on the front face of the back plane, to establish the internal connections. Typically the external cable connectors are affixed along the rear edge of a separate circuit board which is inserted into the rear of the mounting frame, the front edge of which supports a row of contacts that mate with a connector supported on the rear face of the back plane, to establish a connection between the rear circuit board and the front circuit board. This type of system is well known to those skilled in the art.
However, the various devices utilized in such electronic equipment are subject to breakdown, upgrading, changes in system requirements and other circumstances which require that a circuit board be removed from the mounting frame and replaced with another circuit board. In conventional equipment this requires that power to the mounting frame be deactivated, to avoid the possibility of a live conductor contacting a conductor on the circuit board and damaging the delicate components of the circuit during removal or insertion. Further, all of the cable connections to the affected device must be disconnected before the rear portion of the circuit board can be removed, because the cable connectors are attached to the circuit board.
In order to provide a conventional connector for the internal connections such as data busses and power conductors, the contacts for these internal connections are provided along the Tear edge of the circuit board (which is the leading edge as the board is mounted into the mounting frame), so that the contacts approach the connector in the direction of insertion of the board. However, it is desirable to provide as many external cable connectors as possible within the limited space along the rear edge of each circuit board, which does not leave room along the rear edge for contacts for the internal connections. Size constraints do not permit the rear edge of the circuit board to be lengthened to accommodate internal connections, because space is used very sparingly in such facilities.
The internal data busses and power conductors can be connected to a row of contacts along the bottom edge of the circuit board. It is possible to wire a multi-pin connector in alignment with the track, so that when the circuit board is fully inserted into a compartment the connector pins align with the appropriate contacts along the bottom edge of the circuit board. However, this would still require that the power be deactivated before a circuit board is removed, to prevent a data or low power contact brushing past a live power supply pin. Further, the cables connected to the cable connectors along the rear edge of the circuit board must all be detached in order to remove the circuit board.
This presents a problem when a circuit board must be replaced while the equipment is in use, and a significant inconvenience when upgrading or changing circuit boards during equipment down-times.
The present invention overcomes these disadvantages by providing a modular mounting system which allows a circuit board to be removed, inserted or replaced through the front of the mounting frame without deactivating power to the equipment, and in the preferred embodiment without detaching any external cables. The mounting system of the invention achieves a high packaging density for mounted devices and accommodates any input/output format.
In the mounting system of the invention connections for external equipment are disposed along the rear edge of the circuit board, and a row of contacts for the internal connections is provided along the bottom edge of the circuit board. The system of the invention provides a releasable connector which retracts the connector pins into a housing when a circuit board is inserted or removed, thus eliminating the possibility of a contact on the circuit board touching a live connector pin. In the preferred embodiment the external connections are made through adaptors that plug into the external cable connectors, which are provided on a separate plate detachably affixed to the rear of the mounting frame.
In the preferred embodiment the invention provides an actuating mechanism for the releasable connector which must be actuated in order to remove a circuit board, thus ensuring that the connector pins have disengaged from the circuit board contacts before a circuit board is moved.
In another preferred embodiment the invention permits use of two or more separate circuit boards for a device, residing in the same compartment and connected by an interface, which allows circuit boards to be repaired or upgraded by replacing a portion of the device circuitry.
The invention also provides a novel system for cooling the mounting frame, providing heat sink tunnels in the impeller airstream and affixing the most significant heat-generating components to the heat sink. The impeller draws an intake airstream through a low resistance path within the mounting frame to cool the circuit board components, the most problematic heat-generating components on the circuit boards preferably being positioned directly in the path of the impeller intake.
The present invention thus provides a circuit board mounting system for mounting at least one circuit board, comprising a mounting frame having at least one compartment, the compartment having at least a first track for slidably receiving a circuit board, at least one opening through an end of the mounting frame for exposing a rear end of the circuit board supporting at least one external connector, and an internal connector disposed in alignment with the track for engaging against at least one contact disposed adjacent to an edge of the circuit board adjoining the rear edge, wherein when the circuit board is inserted into the compartment the at least one contact is coupled to the internal connector and the external connector is accessible through the opening in the mounting frame.
The present invention further provides a releasable connector for coupling at least one pin to at least one contact on a circuit board, comprising a housing to which the pin is mounted, and a receiving portion adapted receive an edge of a circuit board, a contact arm of the pin being movable between a closed position in which at least portion of the pin impinges into the receiving portion and an open position in which the contact arm is retracted from the receiving portion, and means for moving the contact pin between the open position and the closed position.
In a further aspect of the invention the connector is provided with a plurality of pins, each pin having a contact arm movable between the closed and open positions, and the means for moving the contact arms comprises a cam strip disposed longitudinally through the housing having cams extending toward the contact arms, wherein by moving the cam strip longitudinally in one direction the cams depress the contact arms to the open position, and by moving the cam strip longitudinally in another direction the contact arms return to the closed position.
The present invention further provides a circuit board mounting system, comprising a circuit board having a rear end supporting at least one external connector comprising a first adaptor portion, a mounting frame having at least one compartment, the compartment having at least one track for slidably receiving a circuit board, at least one opening through a first end of the mounting frame for exposing the rear end of the circuit board, and a connector plate supporting at least one cable connector on an exterior face and supporting at least one second adaptor portion on an interior face electrically coupled to the cable connector, the connector plate being disposed over the opening, wherein when the circuit board is mounted into the mounting frame through a second end opposite the first end, the first adaptor portion is coupled to the second adaptor portion to electrically couple an electrical circuit supported by the circuit board to the cable connector.
The present invention further provides an electronic device, comprising a first circuit board supporting a first portion of a circuit for the device, a second circuit board supporting a second portion of a circuit for the device, and a rigid interface adaptor electrically coupling the first circuit board to the second circuit board, wherein the interface adaptor maintains the first circuit board in substantially rigid alignment with the second circuit board to form an integral circuit board.
The present invention further provides a circuit board for an electronic device adapted to be mounted in a mounting frame, having at least one internal connector for electrical connection to at least one other circuit board in the mounting frame and at least one external connector for electrical connection to at least one device external to the mounting frame, wherein the internal connector is disposed adjacent to a first edge of the circuit board and the external connector is disposed adjacent to a second edge adjoining the first edge.